Method of producing powdered titanium and titanium alloys



June 30, 1959 G. F. DAVIES ETAL 2,892,697

METHOD OF PRODUCING POWDERED TITANIUM AND TITANIUM ALLOYS 7 Filed April 19, 1954 I 2 Sheets-Sheet 1 RAW MATERIAL TL4 TO+3O MESH 7 DISTILLED WATER ICE WAT ER BATH n 4 3 F'CH'RI'I'ION Ml LL I3' I v 6 CLASSI Fl ER SETTLI NG TANK FILTER DRIER TITANIUM POWDER PRODUCT F I INVENTORS GAIL E DAVIES HARRY W. DODDS BY y 447 441440 June 30, 1959 G. F. DAVIES ET AL METHOD OF PRODUCING POWDERED TITANIUM AND TITANIUM ALLOYS Filed April 19. 1954 2 Sheets-Sheet 2 INVENTORS GAIL E DAVIES HARRY W. 00005 BY AGENT ilnited States Patent METHOD OF PRODUCING POWDERED TITANIUM AND TITANIUM ALLOYS Gail F. Davies, Willoughby, and Harry William Dodds, Bay Village, Ohio, assignors to Clevite Corporation, Cleveland, Ohio, a corporation of Ohio Application April 19,1954, Serial N0.'423',924

8 Claims. v(Cl. 75-.5)

This invention relates broadly to a process of producing a finely divided metal powderssuitable for use in powder metallurgy. Theprocess is applicable to the. production of powders from titanium metal and titanium met-a1 alloyed with other metals. 7

An important object of this invention is the use of a I new and novel grinding process for -the production of finely divided titanium metal and titanium alloypowders from massive metaL-metal chips and sponge without substantially increasing the oxgen and nitrogen gas content.

titanium metal and titanium alloy powders frommassive metal, metal chips and sponge by grinding such that substantially no foreign elements, such as metal filings are introduced.

A further object of this .inventionisto increase in the grinding operation the internal work energy level of the titanium metal and titanium alloyp'owder-particles, produced from-massive metal, metal chips and sponge,

to obtain betterparticle bonding insintered compacts.

produced from said powder and having characteristics.

A further object of this invention is the production of titanium metal and titanium alloy powders of-substantially uniform particle size from massive metal,-metal chips and sponge.

A further object of this invention is to providea continuous process-for the production of titanium metal and titanium alloy metalpowders of substantially uniimproved strength form particle-size from massive metal, metal chips and sponge substantially without increasing the oxygen and nitrogen-gas content and without introducing foreign metal filings.

The invention relates more specifically to the production of ductile titanium metal and titanium alloy powders having properties suitable for use in the manu facture of metal articles by powder metallurgy techniques.

The foregoing and other objects of the invention will 'be best understood from the following description of A further objectof this invention is theproduction-of exemplifications thereof, reference being had to the accompanying drawings wherein:

Fig. 1 shows a flow diagram of one manner of carrying out applicants novel 3 process.

Fig. 2 is a sectional plan view of an attrition mill suitable for comminuting titanium and-titanium alloys.

Titaniums increasing tendency to actively absorb and react with oxygen and nitrogen as its temperature is; elevated is Wellknown.

2,892,697 Patented June 30, 1959 2. While titanium metal possesses certain distinctly advantageous physical and mechanical properties, the com- ,mercial exploitation of this metal has been seriously re- -metal and the greater surface area exposed serve to increase the, activity of thevmetal toward oxygen and nitrogen resulting in contamination of the powder product with thesegases as shownin Table I to follow.

.When an oxygen and nitrogen contaminated powder is consolidated into an article, by powder metallurgy techniques whereinsintering is effected, the oxygen and nitrogen diffusethroughoutthe article with resultant embrittlement and 'reduction of endurance ratio and ductil- Qity. About 03% oxygen is considered the maximum tolerable-in order to obtainlimited ductility while 'nitro ,gen content greater thanabout 0.03% is considered in the detrimental range.

In contrast to-previous methods of producing powders ,of-titanium and alloys thereof, there has been discovered a-=process of producing these powders, "from massive metal, metal chips and sponge, substantially without increasing the oxygen and nitrogengas content and without -decreasing ductility, by comminuting substantially uniform sized particles of themetal while submerged in ice water. Substantially uniform sized particles is intended toconnote that ai'major portion of the starting material j is-jof;a uniform size {capable of passing through a 4-mesh screen and being retained on a -30-mesh screen.

Further advantages :will be readily apparent from the following description of one embodiment of applicants novel process.

Referring to the drawings: Fig. 1 serves to illustrate in flow sheet form one embodiment of the new and novel a process.

"Substantially uniform sized titanium particles are introduced from storagel into an ice water bath 2, along with distilled water, and are discharged from an outlet in the lower part of the ice water bath to an attrition :mill S via conduit 3. A magnet l may be positioned adjacent the outlet to entrap any iron particles which may be present in the metal particles due to a previous operation and to prevent any iron impurity from passing into the finished metal powder. In the attrition mill 5, V Fig. 2, the comminution and attritioning of the metal particles to powder takes place between two vertically positioned concave circular plates 17, preferably made of titaniumtor an alloy thereof. The comminution and attritioning of the metal takes place while submerged in ice water which substantially completely shields the metal surfaces from ambient gases. The sized metal is introduced into the concavity 18 between the plates through an inlet1'9;positionedcentrally of a stationary plate 170:.

The other of said'pla'tes 17b is mounted in opposed, ad-

"justably spaced relationship to the stationary plate and 05 "is adapted to be rotated about its axis of rotation by 3' means of a prime mover. The rotating plate 17b is adjustably spaced from the stationary plate 17a in a direction along the axis of rotation in an amount such that the outer edges of the plates are separated, by a distance equal to the largest particle diameter permissible in the finished metal powder, forming an escape space 20.

The metal particles, after being reduced to powder by the attritioning action of the plates 17 and by other particleszleave the concavity of the plates 18 through the space 20 between the edges of the plates. Some particles may assume plate-like configuration and being of proper size in one dimension may pass through the space. The metal powder then flows in the ice Water carrier through conduit 6 to classifier 7 where any oversized particles are screened out and returned to the mill via 13. The screened powder along with the ice water then flows via conduit 8 to a settling tank 9 containing crushed ice and water Where the metal powder is allowed to settle, and separate from the supernatant ice water carrier. The settling tank may be cooled by a refrigerated cooling jacket 14. The wet powder is then filtered in filter 11 and finally dried in drier 12 and recovered. The supernatant ice water from the settling tank and the filtrate from the filter are recycled to the ice water bath 2 via conduit 10, and with sufiicient distilled water added to make up for any losses in the system.

For best results in the physical characteristics of the metal powder as well as articles compacted therefrom, the temperature of the water should be maintained as low as possible with ice and/or mechanical refrigeration. Temperatures as high as 5.0 C. have been used with success; however, temperatures below 50 C. are preferred. The use of temperatures above about C. are accompanied with excessive oxygen and nitrogen pickup, under the same conditions, exceeding the limits considered acceptable for obtaining limited ductility. While distilled water is preferred as the comminution blanketing and cooling medium, other materials such as aqueous solutions of NaCl, Na S, Na CO NaOH and hydrazine have been used. Where a salt solution is used the finished metal powder is leached to remove excess salt.

The feed metal is preferably of substantially uniform particle size capable of passing at least a 4-mesh screen and preferably a IO-mesh screen and remaining on a 30- mesh screen. Where the starting material is titanium metal sponge, low density sponge is preferred over high density sponge due to less instantaneous heat being developed during grinding and consequent lower activity toward oxygen and nitrogen. Low density sponge is defined as that weighing less than about nine pounds per gallon. While feed sized to 10 to +30 mesh is preferred substantially uniform sized feed up to -4 mesh has been used with success. A negative sign indicates passes throug and a positive sign indicates retained on the screen. The use of feed size greater than -4 mesh produced galling and welding resulting in lowered efiiciency and excessive oxygen and nitrogen pickup. When a substantially uniform sized feed is used the parlurgical grade powder in all cases.

4 ticle size of the finished powder is substantially uniform, -80% being of a size greater than -100 mesh. When fines below 325 mesh are removed from the powder the remaining powder constitutes 97-98% of the original metal treated as useful product for the production of metal articles by powder metallurgy techniques.

The attritioning plates in the grinder are preferably made of substantially the same metal as that being treated to avoid contamination of the finished powder with foreign metal filings.

The advantages of using a comminuting and cooled excluding medium are that atmospheric oxygen and nitro gen are substantially excluded from the reduced metal particles and that it acts as a heat transfer medium tocarry away the heat developed in the size reduction of the metal particles. The comminuting medium further may act as a lubricant in the comminution. The exclusion of the atmosphere by the comminuting medium serves to prevent contamination of the metals by the excluded atmospheric gases and the control of temperature serves to reduce the activity of the metals toward gases occluded by the grinding medium as well as excluded gases.

The cooling effect of the cooled comminuting medium substantially increases the work energy level of the comminuted metal particles. Subsequent sintering is accelerated due to increased internal energy of the metal particles and, due to better particle bonding, results in a product displaying ductility and uniformity normally experienced only with work hardened and annealed composites.

The following examples show the size distribution and relative oxygen and nitrogen content of Ti metal powdered by air comminuting and comminuting under ice water according to the present invention.

TABLE I Sponge titanium comminuted in air, showing effect of particle size on the amount of gas contamination Run Feed Matl Reduced Percent Percent Percent Size 0 N H Sponge as received 09 .014 .0023

15 Sponge, Lo density.. 60 mesh... 682 .0406 .009

14 do l00 mesh-- 694 078 0153 12 d0 200 mesh 1. 74 037 040 The gas pickup content of the air comminuted samples is excessive. Compacts consolidated from these powders were too brittle to be of metallurgical value.

Table II shows a series of runs made on titanium sponge according to this invention utilizing ice water at a temperature of less than 5 C. Duplicate ice water grinds on low density sponge resulted in a usable metal- It will be noted that run 32, wherein the material was ground to a greater degree of fineness showed a greater oxygen. content. Runs 31 and 32 were both prepared from high density sponge and showed the greatest contamination.

TABLE II Titanium sponge reduced to powder in attrition mill under ice water showing particle size distribution and gas content Percent Percent Percent Percent Percent Percent Percent Percent Percent Run Feed Matl 6 15 -200 325 O N H +60 +100 +200 +325 Sponge as received.... 09 014 0023 31 maggot- 10 mesh (H1 73.2 14.2 4. 7 3.0 2 2. 8 33 009 .012

ensl y 33 Sponge 10 mesh (Lo 68.3 18. 3 5. 8 3. 3 2.1 2.1 .095 017 009 density ftsa'rnpl'es' of the =above ice -watefireduced powdersand had excessive ameunts bfgas centamma on 'these'-'could 1: sample of" air com1flinuted sponge were-consolidated nbtrb'e used. sciap cfitainiiig in' excess ar on-ea -O '"'-1nto-a so1id block'by hot pressing under 0.0005 Hg a1id 103%N is-not co'tisideredfsliitable for the production vacuum at 1000" "Cat" 1000 p.s.i. for 8 hours" and the 'of lisablealloypowder. The aHtiy RG-IBOA was chosen following data obtained: 5 as representative of an alloy scrap h'aving "retained metal- TABLE III Tensile properties and 1 analysis Y of ice water" reduced titanium sponge hot consolidated .Yleld Percent Percent Percent Percent Percent Tensile X p.s.i.Eong. lnRed.in 0 -H N X10 p.s.l. 85 in Area 79. 7 61. 2 27. 1 38. 8 0. 131 0.0018 0. 017 "R0033: -'30+150 mesh 79.8 60.9 27.6 38.1

81.2 62.3 27.1 35.6 0.131 0.0037 0.015 Run 34: -+325'mesh 79.7 61.3 25.9 38.2 i 79.8 61.3 28.2 41.0

TABLE IV Typical tensile properties of -30 mesh air comminuted titanium metal sponge hot consolidated U.H. Yield Percent Percent Tensile X10 'Elong. in Red. in Percent Percent Percent X10 p.s.i. 0.85 in. Area 0 H N p.s.i.

83. 3 65.2 15. 8 30 mesh air mutilated sponge...-- 87. 7 68.9 24. 7

It is significant that in each of the ice water reduced samples there is a decrease in tensile strength and yield lurgical properties suitable for powder metallurgy use. strength and an increase in elongation and reduction Table VI shows composition and properties of a repin area over the air comminuted samples. resentative sample of RC-130A as received and reduced Table V shows the typical composition of titanium by air mutilation and ice water grinding. alloy scrap as received. Since the composition varied Table VII shows the particle size distribution of the from one batch to another and some as received scrap ice water ground RC-130A sample of Table VI.

TABLE V Typical composition of titanium alloy scrap as received Pelrient Percent; Percent Percent Percent Perocent PercentO PercentN PercentH 0 Mn Fe Al Sn RC-130A 6-8. 5 1-. 25 154-. 309 0064-. 035 0014-. 0035 RG-130B 3. 5-4. 5 1. 25 3. 5-4. 5 118-1. 2 01-. 061 005-. 0068 T1 1 so A 1. 3 03-2. 5 0. 58 089 0096 T1 150B 3. 5-4. 8 3. 9-5. 1 3. 9-5. 1 258 079 0019 TABLE VI Tensile properties and analysis of ice water ground and air mutilated RC-l30A titanium alloy Tensile Yield Percent Percent Percent Percent Percent X10 p.s.i. X10 1).s.i. ifllong. Red.in O N H in. Area 140 3. 0 6.5 259 .027 .0009 110-130A Crescents as received. 143 122 27 014 035 ii? E8 go 9% 224 8 o 35 .5 .02 1 Ice Water Gmmd 144 110 e. 0 7.1 .262 .018 .0092 Air Mutilated Lac-A 114 112. 5 0. 5 0. 7 .304 .026 .0243

TABLE VII Particle size distribution RC-130A-ice water ground Ti alloy Mesh --30 +60 60 +100 --100 -150 +200 -200 +325 325 Percent..... 58. 14 26. 43 6. 76 3. 58 2. 54

tion shall not be limited to the specific exemplifications shown or described therein, but only by the scope and spirit of the appended claims.

We claim:

1. In a method of producing ductile powdered titanium and titanium alloys the step of comminuting substantially uniform sized particles thereof while submerged in an atmosphere excluding blanket of a liquid medium substantially inert to titanium and titanium alloys and being adapted to eifectively dissipate the heat developed in the comminution, said liquid medium being at a temperature below C.

2. In a method of producing ductile metal powders of titanium and titanium alloys, the step of comminuting substantially uniform sized particles thereof while submerged in ice water.

3. In a method of producing ductile metal powders of titanium and titanium alloys, the step of comminuting particles thereof within the range of +30 mesh to 4 mesh while submerged in ice water.

4. In a method of producing ductile metal powders of titanium and titanium alloys, the step of comminuting particles thereof within the range of +30 mesh to 4 mesh while submerged in ice water maintained at a temperature below 5.0 C.

5. In a method of producing ductile metal powders of titanium, the step of comminuting particles thereof within the range of mesh to 4 mesh while submerged in ice water maintained at a temperature below 5 C.

6. The method of claim 5 wherein the titanium particles are low density sponge.

7. In a method of producing ductile metal powders of titanium, and titanium alloys, the step of comminuting 10 particles thereof within the range of +30 mesh to -4 mesh while submerged in ice water maintained at a temperature below 5 C., the comminution of said particles being carried out by attrition by active surfaces composed of a metal selected from the grou consisting of titanium and titanium alloys.

8. The method of claim 7 wherein the titanium particles are low density sponge.

References Cited in the file of this patent UNITED STATES PATENTS 1,569,484 Hall Jan. 12, 1926 2,189,640 Powell Feb. 6, 1940 2,259,457 Croll Oct. 21, 1941 OTHER REFERENCES Powder Metallurgy, page 113. Edited by Wulfi. Published in 1942 by the American Society for Metals, Cleveland, Ohio. 

3. IN A METHOD OF PRODUCING DUCTILE METAL POWDERS OF TITANIUM AND TITANIUM ALLOYS, THE STEP OF COMMINUTING PARTICLES THEREOF WITHIN THE RANGE OF +30 MESH TO -4 MESH WHILE SUBMERGED IN ICE WATER. 